Known variable valve timing control devices are disclosed in Japanese Patent Nos. 3266013 and 3146956. The disclosed variable valve timing control devices each include a housing member integrally rotating with one of a crankshaft and a camshaft of an internal combustion engine, a rotor member assembled to the housing member so as to be rotatable relative thereto and being slidable on a concave portion formed on the housing member. The rotor member includes vane portions each forming an advanced angle chamber and a retarded angle chamber within the housing member, and integrally rotating with the other one of the crankshaft and the camshaft. The variable valve timing control device also includes a stopper formed on the convex portion and being in contact with at least one of the vane portions for restricting the relative rotation between the housing member and the rotor member to an advanced angle side or a retarded angle side. The variable valve timing control device further includes a lock mechanism for restricting the relative rotation between the housing member and the rotor member by a lock member formed on the housing member to be inserted into a receiving hole formed on the rotor member when a relative rotation phase between the housing member and the rotor member is positioned at a predetermined phase, and a fluid pressure circuit for controlling an operation oil to be supplied to or discharged from the advanced angle chamber, the retarded angle chamber, and the lock mechanism.
According to the variable valve timing control device disclosed in Japanese Patent No. 3266013, when the lock member is in contact with an opening edge portion of a receiving hole within which the lock member is positioned, plastic flow of material forming the receiving hole may be caused due to tangential stress. Then, the opening edge portion may be raised towards the housing member side. Further, the opening edge portion being raised may interfere with the relative rotation between the housing member and the rotor member. In order to address the above problem, the lock member includes an engaging taper face on a side of the receiving hole while the receiving hole includes a guiding taper face gradually expanding towards an opening side of the receiving hole. The lock member is in contact with an inner peripheral face of the receiving hole under the condition that a taper angle of the guiding taper face is larger than that of the engaging taper face. Then, the plastic flow may be prevented from occurring in the opening edge portion of the receiving hole.
In addition, according to the variable valve timing control device disclosed in Japanese Patent No. 3146956, a clearance is formed between the lock member and the receiving hole considering a receiving performance of the lock member in the receiving hole. When the advanced angle chamber or the retarded angle chamber is not sufficiently supplied with the operation fluid from an oil pump at a time of an engine start, the rotor member and the housing member starts rotating relative to each other due to the fluctuation torque of the cam being applied. At this time, since the clearance is formed between the lock member and the receiving hole, an inner periphery of the receiving hole and an outer periphery of the lock member may become in contact with each other repeatedly, thereby causing a hitting sound. In order to address the above problem; a taper face is formed on at least one of the lock member and the receiving hole being in contact with each other. Then, a biasing force to bias the rotor member in the rotational direction is generated in the housing member to strongly press the stopper and the vane portion to each other so that the rotor member and the housing member are constrained at a locked position.
According to the variable valve timing control device disclosed in Japanese Patent No. 3266013, the lock member can be in contact with the inner circumferential face of the receiving face. However, a clearance may be formed between the lock member and the receiving hole, which causes a looseness therebetween. Further, the hitting sound due to the looseness may occur.
In addition, according to the variable valve timing control device disclosed in Japanese Patent No. 3146956, the rotor member and the housing member are constrained at the locked position and thus the lock member may not be able to move from the receiving hole.
Thus, a need exists for a variable valve timing control device which can prevent an occurrence of hitting sound due to a relative rotation between a lock member and a receiving hole in case of the relative rotation being locked.
A need also exists for a variable valve timing control system in which the lock member is prevented from being constrained in the receiving hole when the locked state of the relative rotation is released.